Lighting systems are well-known and are used in a wide variety of applications, including automotive applications. Generally, an automotive headlamp, for example, includes a light source and optical components, such as lenses and reflectors to collect and shape light emitted by the light source and to project the resulting beam pattern forward of the vehicle in a light distinct pattern. It may be preferred that a single automotive headlamp system be capable of projecting more than one beam pattern (i.e. a bi-functional headlamp). For example, a headlamp may emit light in a low-beam mode in which light is generally emitted below the horizon. The headlamp may also emit light in a high beam mode in which light is generally emitted above and below the horizon.
Some bi-functional headlamp systems include multiple light sources for the low and high beam modes. For example, some filament headlamp systems include multiple filaments: one filament for the low beam function, and another filament for the high beam function. Similarly, some light emitting diode (LED) headlamp systems include multiple strings of LED modules or chips; one string of LEDs for the low beam function, and another string of LEDs for the high beam function. Some headlamp systems further include a mechanism for adjusting the light sources and/or other components of the headlamp, such as the reflector, to produce the low beam and high beam functions. Additionally, some bi-functional headlamp systems, such as, for example, a projector headlamp, utilize a single shutter or light shield to selectively block a portion of the light from a single light source to provide a low beam pattern and, to provide a high beam pattern, the shielded light is added to the beam by retraction of the shield. Examples of headlamp reflectors are found in U.S. Pat. No. 7,896,532 (Hsu) and U.S. Patent Pub. No. 2009/0296418 (Luo).
These types of known bi-functional headlamp systems have limitations. For example, one drawback associated with bi-functional headlamp systems having multiple light sources is the amount of space required for each light source. More specifically, each discrete light source (e.g., low-beam light source, high-beam light source) generally requires an associated compartment, or cavity, to house and contain each light source and, in some cases, an associated reflector, within. Although projector headlamps may require less space than multiple light source headlamps (due to the use of a single light source), projector headlamps are limiting with respect to styling options and are generally less efficient and provide lower performance when compared to reflector headlamps, particular in low-beam mode.
For a thorough understanding of the present disclosure, reference should be made to the following detailed description, including the appended claims, in connection with the above-described drawings. Although the present disclosure is described in connection with exemplary embodiments, the disclosure is not intended to be limited to the specific forms set forth herein. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient. Also, it should be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.